Effects of Very Low-calorie Diet Versus Bariatric Surgery on Body Composition and Gut Microbiota Pattern

Effects of Very Low-calorie Diet Versus Bariatric Surgery on Body Composition and Gut Microbiota Pattern in Obese Patients

Obesity is a chronic disease characterized by the excessive accumulation of fat in body and it continues to be a major public health problem worldwide. Treatment options for obesity include lifestyle modification, pharmacotherapy and bariatric surgery. Bariatric surgery is a highly effective treatment for obesity and results in rapid and sustained weight loss. Also, it significantly alters gut microbiota composition and function. A very low-calorie diet (VLCD) is a rapid weight loss program which calorie intake is severely restricted (< 800 kcal/day). It has been shown to be very effective to induce rapid weight loss and result in comorbidities resolution similar to bariatric surgery. Therefore, this study was aimed to study the effects of 12-week VLCD compare to bariatric surgery (Laparoscopic Roux-en-Y gastric bypass (LRYGB) or Laparoscopic Sleeve Gastrectomy (LSG)) on weight loss, body composition, gut microbiota pattern and other metabolic parameters.

The study will include obese patients (body mass index; BMI ≥ 37.5 kg/m2 or BMI ≥ 32.5 kg/m2 with comorbidities), aged 15-65 years at Ramathibodi Hospital, Thailand. The VLCD group will received total diet replacement for 12 weeks and the bariatric surgery group will undergo LRYGB or LSG. Study participants in both groups will be matched according to their age, sex, body mass index (BMI) and diabetic status. Body weight reduction and body composition, gut microbiota pattern, liver stiffness and steatosis, glycemic and other metabolic parameters (glucose, insulin, c-peptide, lipid profile, liver function test, kidney function test, complete blood count, electrolyte blood test, thyroid function tests, serum ketone and adiponectin), health-related quality of life, depression score and twenty-four-hour diet recall and physical activity will be assessed at baseline and at month 1, 3, 6, 9 and 12.

Inclusion Criteria:

• Aged 15-65 years
• Male or female
• Body mass index ≥ 32.5 kg/m2 with obesity related co-morbidity
• Body mass index ≥ 37.5 kg/m2 with or without an obesity related co-morbidity

Exclusion Criteria:

• End stage disease such as cancer, cirrhosis Child-Pugh C, critical/acute illness
• Type 1 diabetes mellitus
• Recent eGFR < 30 ml/min/1.73 m2
• Weight loss ≥ 5% in the previous 3 months
• Use of antibiotics in the previous 1 month
• Use of probiotic or prebiotic supplement in form of tablet or sachet in the previous 14 days
• Current treatment with anti-obesity drugs
• Pregnancy or breast feeding
• Substance abuse
• Uncontrolled psychiatric disorder and eating order
• History of allergy to any components in meal replacement product or whey protein product
• Unable to give informed consent